Surgical knife safety handle

ABSTRACT

A surgical knife safety device having a handle, a blade connected to the handle, and a guard carried by the handle for sliding movement between a retracted position in which the blade is exposed for use, and an extended position for covering the sharp cutting edge of the blade. In the retracted position, an enlarged guard radius is provided at the distal end of the handle to allow improved handle control and blade orientation. The enlarged guard radius is positioned to allow the user to firmly grip a large distal handle portion which is preferably molded as a single piece with the blade holder, preventing unwanted blade or handle movement due to guard mechanism tolerances.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 12/929,014,filed Dec. 22, 2010, entitled “Surgical Knife Safety Handle”, which is acontinuation of U.S. patent application Ser. No. 11/980,436, filed Oct.31, 2007, entitled “Surgical Knife Safety Handle”, now U.S. Pat. No.7,901,422, which is a division of U.S. patent application Ser. No.10/828,501, filed Apr. 21, 2004, entitled “Surgical Knife SafetyHandle”, now U.S. Pat. No. 7,387,637, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/519,614, filed Nov. 14, 2003,entitled “Surgical Knife Safety Handle”, and which is acontinuation-in-part of U.S. patent application Ser. No. 10/420,614,filed Apr. 22, 2003, entitled “Surgical Knife Safety Handle”, now U.S.Pat. No. 7,022,128, the entire contents of all of said priorapplications being incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a system and method for a surgicalknife safety handle, for both ophthalmic and non-ophthalmicapplications, having a movable guard that can be retracted to expose theblade when in use, and that can be extended to cover the blade when notin use, and including a pushback prevention mechanism to ensure theblade is covered until manually exposed.

BACKGROUND OF THE INVENTION

In various surgical procedures, the physician typically has to make anincision in the patient in order to remove unwanted tissue, repairdamaged tissue, or implant a device to improve the patient's well being.In certain cases, all three of these activities, or a combinationthereof, must be done in a single procedure. For example, in cataractsurgery, the physician removes the natural lens that has been clouded bya cataract from the patient's eye and replaces it with an artificiallens that will improve the patient's eyesight. In order to perform thisprocedure, an incision is made in the cornea of the eye by the physicianusing a scalpel. This provides the physician with access to thepatient's lens. The clouded lens is cut loose and removed. There are anumber of different procedures that are used to remove a patient's lensthat has a cataract. Two of the more common techniques are known asextracapsular surgery and phacoemulsification.

In extracapsular surgery, the physician removes the lens leaving behindthe back half of the capsule. In phacoemulsification, the physicianfragments the lens by ultrasonic vibrations and the lens issimultaneously irrigated and aspirated. After the lens is removed, thephysician then inserts an artificial lens known as an intra-ocular lens(IOL) into the eye either behind or in front of the iris. Two tinyC-shaped arms connected to the IOL eventually become scarred into theside of the eye and hold the IOL firmly in place.

In another type of ophthalmic procedure known as the Implantable ContactLens procedure (ICL), the physician makes an incision in the patient'seye and implants a contact lens in the eye in front of the existing lensbut behind the iris. This corrects the patient's vision so that he orshe can see clearly without the need for external contact lenses oreyeglasses.

Typically a nurse or other surgical assistant manages the devices thatare used during such delicate surgeries. For example, the assistantensures that the appropriate sterile devices are available in theoperating suite for the particular procedure that is to be performed.With respect to scalpels, the nurse often hands the scalpel to thephysician in a predetermined orientation so that the physician can gripthe scalpel's handle without taking his or her eyes away from thepatient. This also minimizes the possibility that the physician will becut with the blade on the scalpel. After the physician completes theincision, the scalpel is handed back to the assistant for properdisposal or sterilization. While the procedure is being performed, thisrequires the assistant to place the used scalpel on a particular traythat will be removed after the procedure is completed. The devices onthe tray are then disposed of or are sterilized for reuse.

If all appropriate protocols are followed, no hospital personnel will becut by used or unused scalpel blades. Unfortunately, accidental cuts ofhospital personnel do occur for a variety of reasons. For example,because the physician and assistant are concentrating on the patient andthe procedure being performed on the patient, they may not pay closeattention to the scalpels. The assistant may put the used scalpels in aninappropriate location or, even if the used scalpels are placed on theproper tray, the blade may be exposed to the operating suite personnel.In these situations, the operating suite personnel may inadvertentlycome into contact with the blade as they move around the patient duringthe procedure and be cut or nicked by the exposed blade.

Other hospital personnel may also come into contact with such blades andmay also be cut or nicked. Usually used blades are disposed of in anappropriate sharps container that allows used needles and blades to beinserted into the container but prevents access by hospital personnel tothe sharp end of a needle or the sharp cutting surface of the blade.However, during cleanup of the operating suite, the used blades may beexposed prior to their placement in the appropriate sharps container. Ifhospital personnel are not paying close attention to their activitiesor, if the exposed blades are hidden from view because they are buriedin a pile of other devices or hospital linen, these hospital personnelmay come into contact with the sharp cutting surface of the blade and becut or nicked.

Cuts and nicks from blades are uncomfortable and distracting at best. Inaddition, such cuts and nicks from used blades may result in blood orbody fluid exposure which can result in the spread of infectiousdiseases between the patient and hospital personnel. Concern over thissituation has become especially acute in recent years because of suchdiseases as acquired immuno-deficiency syndrome, i.e. AIDS, andhepatitis. These diseases may be transmitted from an infected person toanother person by the transmission of body fluids, typically blood.

In view of the need for a scalpel that can at least minimize the chancesof accidental cuts or nicks, while also protecting the cutting edge ofthe blade, numerous scalpels have been designed. These designs typicallytake the form of a scalpel having a guard that shields the sharp cuttingsurface of the blade from undesired contact with hospital personnel andsurrounding surfaces. The guard in these devices can be extended to aposition shielding the blade or retracted exposing the blade for use.Alternatively, the scalpel may be designed to allow the blade to moveinto or out of the scalpel handle, to either shield or expose the sharpcutting surface.

Unfortunately, these designs are deficient because they tend to becumbersome, difficult to use, may cause unwanted shielding or exposureof the blade prior to the need for such shielding or exposure. Also,such devices may require considerable attention by the user to shield orexpose the blade. Additionally, the shield may distort the handleoutline when retracted, making the handle difficult to hold or control.Any design which allows the blade to move, for retraction or extensiondesign purposes, also introduces concerns regarding exact bladepositioning and rigidity during use. Such concerns also apply in casesin which the user is required to hold the retracted shield as a grip,allowing any movement between shield and handle to possibly result inunwanted movement of the blade.

Accordingly, a need exists for a device and method to provide ashielding mechanism that is simple to use and remains locked in ashielding position until disengaged by the user mechanism. The handleand shielding mechanism must also provide a uniform gripping surfacewhen retracted, allowing user control of the scalpel without anyunwanted gripping surface or blade movement.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a device andmethod that may be used to shield and protect a sharp blade, such as ascalpel, and minimize the chances of cuts or nicks during handling ordisposal.

It is another object of this invention to provide a device and methodthat is easy to use and that can be operated by one hand of the user.

It is another object of the invention to provide a device and methodthat will not allow the shield to be accidentally displaced when fullyextended and expose the blade.

It is another object of this invention to provide a device and methodwhich maintains an uninterrupted handle surface contour during use,which allows the user better control and orientation of the device.

These and other objects are substantially achieved by providing a deviceand method for a handle, a blade connected to the handle, and a guardslidably mounted partially within the handle for sliding movementbetween a retracted position in which the blade is exposed for use, andan extended position for covering the sharp cutting edge of the blade.In the retracted position, an exposed guard radius is provided at thedistal end of the handle to allow improved handle control and bladeorientation. The exposed guard radius however, is positioned to allowthe user to firmly grip a large distal handle portion which is molded asa single piece with the blade holder, preventing unwanted blade orhandle movement due to guard mechanism tolerances.

A leaf spring and detent is provided to fix the guard in the extendedand retracted position, and provide slight resistance during movementbetween each position. Additionally, an antitravel mechanism isincorporated in the guard to prevent accidental retraction from thefully extended position. The above and other objects and advantages ofthe invention will be apparent upon consideration of the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages will be apparent uponconsideration of the following drawings and detailed description. Thepreferred embodiments of the present invention are illustrated in theappended drawings in which like reference numerals refer to likeelements and in which:

FIG. 1 is a perspective view of an embodiment of the present inventionwith the guard in a retracted position to expose the blade;

FIG. 2 is a perspective view of an embodiment of the present inventionwith the guard in an extended position to shield the blade;

FIG. 3 is an exploded perspective view of an embodiment of the presentinvention;

FIG. 4 is a cross-sectional view of an embodiment of the presentinvention taken along line A-A of FIG. 1;

FIG. 5A is a perspective view of an embodiment of the engagement betweenthe guard positioning mechanism and the guard in accordance with anembodiment of the present invention;

FIG. 5B is a cross-sectional view of an embodiment of the engagement endof the guard in FIG. 5A;

FIG. 5C is a perspective view of an embodiment of the engagement end ofthe guard in FIG. 5A;

FIG. 5D is a cross-sectional view of an embodiment of the engagement endof the guard positioning mechanism in FIG. 5A;

FIG. 5E is a perspective view of an embodiment of the engagement end ofthe guard positioning mechanism in FIG. 5A;

FIG. 6 is an enlarged cross-sectional view of an embodiment of the guardpositioning mechanism and the guard in accordance with an embodiment ofthe present invention taken along line B-B of FIG. 1;

FIG. 7 is an enlarged cross-sectional view of an embodiment of the guardpositioning mechanism and the guard in accordance with an embodiment ofthe present invention taken along line C-C of FIG. 1;

FIG. 8A is a cross-sectional view of a second version of the embodimentof FIG. 1 illustrating a guard positioning mechanism having an integralspring;

FIG. 8B is an enlarged cross-sectional view of the detent engagement ofthe integral spring of FIG. 8A;

FIG. 8C is an enlarged cross-sectional view of the detent engagement ofthe leaf spring of FIG. 3;

FIG. 8D is a side view of the guard positioning mechanism and integralspring of FIG. 8A;

FIG. 8E is a bottom view of the guard positioning mechanism and integralspring of FIG. 8A;

FIG. 8F is a perspective view of the guard positioning mechanism andintegral spring of FIG. 8A;

FIG. 9A is a perspective view of another embodiment of the presentinvention with the guard in a retracted position to expose the blade;

FIG. 9B is a perspective view of the embodiment of FIG. 9A with theguard in an extended position to shield the blade;

FIG. 10 is an exploded perspective view of the embodiment of FIG. 9A;

FIG. 11 is an enlarged cross-sectional view of the embodiment of FIG. 9Ataken along line D-D of FIG. 9A;

FIG. 12A is a perspective view of another embodiment of the presentinvention with a plunger type operator control and the guard in anextended position to shield the blade;

FIG. 12B is a perspective view of the embodiment of FIG. 12A with aplunger type operator control and the guard in a retracted position toexpose the blade; and

FIG. 12C is a perspective view of another embodiment of the presentinvention with a segmented plunger type operator control and the guardin a retracted position to expose the blade.

In the drawing figures, it will be understood that like numerals referto like structures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment of the present invention described below discloses asurgical knife safety handle, for both ophthalmic and non-ophthalmicapplications, having a movable guard that can be retracted to expose theblade when in use, and that can be extended to cover the sharp cuttingedge of the blade when not in use. The guard is located at a distal endof the handle, partially extending from inside the handle, and includinga larger diameter shielding end which becomes part of the exposed handlewhen fully retracted. When fully extended, the guard covers the exposedcutting edge of the blade without distorting handle contours. The guardis engaged with a drive mechanism slidably mounted within the handlebody, which includes a leaf spring for engaging detents at fullyextended and fully retracted positions, and providing audible andtactile engagement feedback. The engagement between the guard and drivemechanism also serves to prevent guard displacement when fully extendedexcept through drive mechanism control.

As shown in FIG. 1, the surgical knife safety handle 10 of the presentinvention includes a body 20 having a guard 30 slideably receivedpartially within body 20 for longitudinal sliding movement between aretracted and extended position. FIG. 1 is a perspective view of anembodiment of the present invention with the guard 30 in a retractedposition to expose a blade 40 for use. The guard 30, when in theretracted position, forms a smooth, uninterrupted handle surface betweendistal and proximal ends, which is preferred by users of such deviceswhen in use. Additionally, the enlarged guard portion, external to body20 when fully retracted, defines a noncircular contour about the distalend of the surgical knife safety handle 10 which gives the user bettercontrol and allows easier blade orientation during use.

As used herein, the term “proximal” refers to a location on the surgicalknife safety handle 10 closest to the person using the device handle andfarthest from the patient in connection with which the device handle isused. Conversely, the term “distal” refers to a location on the devicehandle of this invention farthest from the person using the devicehandle and closest to the patient in connection with which the devicehandle is used.

The surgical knife safety handle 10 of the present invention alsoincludes a blade 40, or similar device, fixedly secured to the distalend of body 20. However, as stated earlier, exposed blades such as thispresent several hazards, including accidental cuts of hospital personneland blade damage. To prevent this, the guard 30 can be slideablyextended from the distal end of body 20 to shield the exposed blade 40as shown in FIG. 2. FIG. 2 is a perspective view of an embodiment of thepresent invention with the guard 30 in an extended position. A leafspring and antitravel mechanism is employed within the body 20 toprevent unwanted movement of the guard 30 when fully extended, asdescribed in greater detail below.

FIG. 3 is an exploded perspective view of an embodiment of the presentinvention. The view of FIG. 3 includes an upper body contour wall 22 anda lower body contour wall 24, formed to assemble as a handle body 20 anddefine a substantially hollow chamber within the body 20 to house aguard positioning mechanism 50 and a concealable portion of guard 30.

The upper body contour wall 22 includes a slot 28 accessing the chamberto allow protrusion of a raised operator control 58 for the guardpositioning mechanism 50, which can be collectively referred to as auser actuator. The distal end of the upper body contour wall 22 alsoincludes an outer surface having a dimpled texture, extending from thedistal end of the upper body contour wall 22 to a point slightly beforethe access slot 28. The textured surface is sufficient to provide theuser with a nonslip grip during use, and is duplicated in a similarposition on the lower body contour wall 24 such that when assembled, thetextured surface appears uniform about an outside diameter of the body20 near the distal end. Although a dimpled surface is shown in theembodiment in FIG. 3, any nonslip surface can be used. Additionally, thenonslip surface can be extended or modified from the area shown anddescribed in FIG. 3 as required in other embodiments.

The distal end of the upper body contour wall 22 further includes asemicircular mating port, extending rearward from the distal end, andproviding a position in which the raised contoured surface of theexposed portion of the guard 30 is seated when fully retracted. In thefully retracted position, the mating port and exposed guard portion ofthe guard 30 are configured to provide the smooth, uninterrupted handlesurface and noncircular contour about the distal end as described above.

The upper body contour wall 22 and lower body contour wall 24 assembleto form the handle body 20 and define a substantially hollow chamberwithin the body 20 to house a guard positioning mechanism 50 and aconcealable portion of guard 30. The guard positioning mechanism 50,which is described in greater detail below and shown in FIG. 5A, has agenerally cylindrical cross section and is sized to slidably fit withinthe hollow chamber within the body 20. The guard positioning mechanism50 is controlled to travel between a fully extended and fully retractedposition via an external protrusion 58 accessed through channel 28. Eachposition is maintained by an engagement between a leaf spring 52, whichis contained within a body cavity of the guard positioning mechanism 50,and either a first or second detent 54 and 56 in the lower body contourwall 24 as described below.

The lower body contour wall 24 includes a first and second detent 54 and56 to engage the leaf spring 52 of the guard positioning mechanism 50,locking the guard in position when fully extended or fully retracted. Asnoted above, the upper body contour wall 22 and lower body contour wall24 assemble to define a substantially hollow chamber within the body 20to house the guard positioning mechanism 50 which contains a leaf spring52, wherein the leaf spring is oriented within the guard positioningmechanism 50 to firmly press against the lower body contour wall 24 whensliding between extended and retracted positions. The lower body contourwall 24 includes a first and second detent 54 and 56, located atopposite positions within the substantially hollow chamber such that theleaf spring engages the first detent 54 when the guard positioningmechanism 50 is in a fully retracted position, and engages the seconddetent 56 when the guard positioning mechanism 50 is in a fully extendedposition. Slidable movement of the guard positioning mechanism 50between positions is opposed with a slight resistance created by theleaf spring 52 contact with the lower body contour wall 24 betweendetents.

The engagement between spring and either detent also provides audibleand tactile engagement feedback to the user. The engagement produces anaudible sound, such as a “click”, when fully extended or fullyretracted, and the spring is properly engaged. Also, the properengagement also produces a mechanical vibration pulse, or tactilefeedback, which allows the user to ensure engagement has occurred.

As shown in FIG. 3, the distal end of the lower body contour wall 24also includes a tapered blade holder 26, or post, configured to fixedlysecure the blade 40 to the distal end of body 20. The tapered bladeholder 26 is molded as an extension of the lower body contour wall 24distal end and has a generally circular cross section area at a point ofattachment, and is tapered slightly to a reduced cross section area at apoint of attachment to the blade 40, which can be epoxy bonded to theholder.

As shown in FIG. 4, the holder 26 is secured to the lower body contourwall 24 distal end via a molded connection spanning approximately 90degrees of the circumference of the generally circular cross sectionarea of the holder 26 at the point of attachment, allowing the guard 30to effectively shield approximately 270 degrees about the axis of theblade when fully extended. FIG. 4 is a cross-sectional view of anembodiment of the present invention taken along line A-A of FIG. 1,showing the point of attachment between the holder 26 and the lower bodycontour wall 24, and the semicircular opening at the distal end of thebody 20 through which the guard is extended and retracted during use.The cross section shown in FIG. 4 also shows the enlarged distal end ofthe guard 30, which is required to provide sufficient clearance for theblade when fully extended. This enlarged distal end is shown as oneexample, an may be modified to accommodate any blade type or guardingpurpose.

In FIG. 4, the molded connection between holder 26 and the lower bodycontour wall 24 provides a first and second slot 27 a and 27 b on eitherside of the holder 26, for use in guiding the guard 30 between extendedand retracted positions and preventing twisting or distortion. Asadditional support for the guard 30, the assembly of body contour walls22 and 24 creates a third slot 27 c between contour wall 22 and theholder 26, linking slots 27 a and 27 b, such that a continuoussemicircular slot is provided at the distal end, about the holder 26,through which the guard 30 travels between fully extended and fullyretracted positions. The guard 30, as described in greater detail below,has a generally semicircular cross section and is sized at a proximalend to extend and retract through the semicircular distal openingprovided by the body 20, and is enlarged at a distal end to surround theblade 40 without interference when extended. The guard 30 can beconstructed of any suitable material, including transparent or opaquepolycarbonate materials. A transparent guard is advantageous in allowingthe user to see the blade 40 even when it is fully shielded by theguard.

In the first embodiment of the present invention, the guard 30 does nothave a fully circular cross section at the distal end due to the moldedattachment of the holder 26 to the lower body contour wall 24. Thisfeature ensures the user is allowed to firmly grip a surface that issingularly molded with the blade holder 26. This presents a morepositive grip which is less susceptible to unwanted blade or grippingsurface movements due to tolerances between the guard 30 and each bodycontour wall 22 and 24. The enlarged distal end of the guard 30 whichremains external to the body 20 when fully retracted however, is rigidenough to provide additional control and blade orientation with one ormore fingers of the user if so desired during use.

FIGS. 5A-5E, 6 and 7 show additional details of the guard positioningmechanism 50 and the guard 30. FIG. 5A illustrates the engagementbetween the guard positioning mechanism and the guard, and FIGS. 6 and 7illustrate an enlarged cross-sectional view of the engagement shown anddescribed in relation to the body 20. FIGS. 5B-5E provide additionalviews of the engagement mechanisms of both the guard positioningmechanism and the guard.

As shown in FIG. 5A, the guard positioning mechanism 50 has a generallycircular cross section and is sized to slidably fit within the hollowchamber within the body 20. The guard positioning mechanism 50 ismechanically engaged with the guard 30 to direct and control guardtravel between a fully extended and fully retracted position. Thecombined length of the mechanism 50 and guard 30 is sufficient to allowa substantial portion of the guard 30 to retract within body 20. Only apartial radius of the enlarged distal end of the guard 30 remainsexposed as shown in FIG. 1.

The guard positioning mechanism 50 is mechanically engaged with theguard 30 via a tapered locking pin located at an engagement end of theguard positioning mechanism 50 and described in greater detail below.The mechanical engagement between positioning mechanism 50 and guard 30allows the positioning mechanism 50 to control the slidable movement ofthe guard 30 between extended and retracted positions. External controlof the guard positioning mechanism 50 is directed by the user via theraised protrusion 58 which extends from within the hollow chamber of thebody 20 via channel 28. The ease of control allows the user one fingercontrol of the positioning mechanism and the attached guard.

As shown in greater detail in FIG. 6, each position of the guard 30 ismaintained by an engagement between a leaf spring 52, located within abody cavity of the guard positioning mechanism 50, and either a first orsecond detent 54 and 56 located in the lower body contour wall 24. Theguard positioning mechanism 50 is substantially hollow and contains aleaf spring 52 which is oriented within the guard positioning mechanism50 with an exposed spring apex extending from the guard positioningmechanism 50 via an opening 60. The spring apex extending from opening60 firmly presses against the lower body contour wall 24 when slidingbetween extended and retracted positions. The lower body contour wall 24includes a first and second detent 54 and 56, located at oppositepositions within the substantially hollow chamber such that the leafspring engages the first detent 54 when the guard positioning mechanism50 is in a fully retracted position, and engages the second detent 56when the guard positioning mechanism 50 is in a fully extended position.Slidable movement of the guard positioning mechanism 50 betweenpositions through the use of a prevailing force is opposed with a slightresistance created by the leaf spring 52 contact with the lower bodycontour wall 24 between detents. The slight resistance provided allowsthe guard 30 to maintain a position when the user releases the externalcontrol 58, and prevents the guard from freely sliding.

As shown in FIG. 5A, the guard 30 extends between a generally circularcross section at a proximal end, and a generally semicircular crosssection at an enlarged distal end. The guard is not fully circular alongit's entire length due to the need to surround the molded attachment ofthe holder 26 and the blade 40, which is in rigid attachment to the bodyvia the lower body contour wall 24. Therefore the guard 30 includesopposite engagement and shielding ends. At the engagement, or proximalend, the guard has a generally circular cross section and is sized toslidably fit within the hollow chamber within the body 20, andmechanically engage the guard positioning mechanism 50 which directs andcontrols the travel of the guard 30 between a fully extended and fullyretracted position as described above. The engagement end of the guard30 is described in greater detail below.

The shielding, or distal end of the guard 30 shown in FIG. 5A, has agenerally semicircular cross section and is sized to extend and retractthrough the semicircular distal opening provided by the body 20. Anenlarged semicircular area, as also shown in FIG. 4, is provided at theextreme end of the distal end of the guard 30 to provide adequateclearance of the blade 40 when the guard 30 is fully extended.Additionally, as noted above, the enlarged semicircular area provided atthe extreme distal end of the guard 30 remains external to the body 20when the guard is fully retracted, and is rigid enough to provideadditional control and blade orientation with one or more fingers of theuser if so desired.

As shown in FIGS. 5B and 5C, the engagement, or proximal end of theguard 30, includes a coupling mechanism having four flanges 34 a, 34 b,34 c and 34 d, to engage the tapered locking pin 62 located at theengagement end of the guard positioning mechanism 50. As shown in FIGS.5D and 5E, the engagement end of the guard positioning mechanism 50includes a tapered locking pin 62 having four surface quadrants 62 a, 62b, 62 c, and 62 d. The coupling mechanism of the guard 30 engages thefour surface quadrants 62 a, 62 b, 62 c, and 62 d of the tapered lockingpin 62 using the four flanges 34 a, 34 b, 34 c and 34 d extending fromthe engagement end of the guard and surrounding a mating opening for thelocking pin 62. Flanges 34 a and 34 c are located on opposite sides ofthe mating opening and are used to engage surface quadrants 62 a and 62c of locking pin 62 to achieve mechanical engagement. Flanges 34 b and34 d are also located on opposite sides of the mating opening and areused to engage surface quadrants 62 b and 62 d of locking pin 62 toachieve antitravel engagement.

Mechanical engagement between guard positioning mechanism 50 and theguard 30 is shown in FIGS. 5A-5E and 6. FIG. 6 is an enlargedcross-sectional view showing the locked engagement between flanges 34 aand 34 c, and pin quadrants 62 a and 62 c. FIG. 7 is an enlargedcross-sectional view rotated 90 degrees relative to the view of FIG. 6,and showing the potential for engagement between flanges 34 b and 34 d,and pin quadrants 62 b and 62 d.

As shown in FIGS. 5 and 6, the locking pin 62 is inserted into thecoupling mechanism of the guard 30 until locked into place by lockingflanges 34 a and 34 c. To engage the guard 30 with the guard positioningmechanism 50, the locking pin 62 is inserted into the four lockingflanges 34 a, 34 b, 34 c and 34 d extending from the body of the guard30. The locking pin 62 is tapered along quadrants 62 a and 62 c,allowing an inner lip 32, located about the inside circumference of twolocking flanges 34 a and 34 c, to displace the flanges outward until theinner lip 32 is disposed into the groove 64 near the base of the lockingpin 62, locking the guard into place. When fully engaged, the inner lip32 engages the groove 64 located about the outside circumference of thelocking pin 62, preventing the separation of guard 30 and guardpositioning mechanism 50. The two locking flanges 34 a and 34 c are madeof a material sufficiently pliant to allow displacement outward due tothe insertion of locking pin 62, yet maintain engagement between theinner lip 32 and groove 64 during movement of the guard positioningmechanism 50.

Antitravel engagement between guard positioning mechanism 50 and theguard 30 is shown in FIGS. 5A-5E and 7. When engaged and fully extended,additional movement of the guard 30 and guard positioning mechanism 50towards one another will engage an antitravel mechanism incorporatedinto the coupling mechanism components described above. Travel of theguard 30 towards a stationary guard positioning mechanism 50 indicates aforce, not properly originating from the user, is acting in a manner toretract the guard. Such forces can result from a number of causes,including external forces applied to the guard when fully extended.Examples include instances where the extended guard 30 is bumped orstruck. Such forces could result in the guard partially retracting andexposing part or all of the blade 40. To prevent this, an antitravelmechanism is engaged when the guard 30 is fully extended, and anexternal force is applied to the guard which would tend to force theguard from the fully extended position against the resistance of theguard positioning mechanism 50.

As shown in FIGS. 5A-5E and 7, the locking flanges 34 b and 34 dextending from the body of the guard 30 each include an inner ramp 36,which engages the surface quadrants 62 b and 62 d of the locking pin 62of the guard positioning mechanism 50 when the guard 30 is moved towardsthe guard positioning mechanism beyond the locking point describedabove. Quadrants 62 b and 62 d include a slight flat along the taper ofthe pin such that in a normal, engaged position, the inner ramp contacts36 do not displace the flanges 34 b and 34 d. However, while fullyextended, if there is an external force applied to the guard 30, forcingthe guard towards the guard positioning mechanism 50, the pin surfacequadrants 62 b and 62 d engage the ramps 36 and the locking flanges 34 band 34 d are displaced in an outward direction, against the inner wallsof the hollow chamber within the body 20. As the flanges 34 b and 34 dare displaced, each contacts a groove 38, located along the inner wallof the chamber. The flanges 34 b and 34 d, once fully displaced withinthe groove 38, travel along the groove a minute distance untilcontacting a shoulder at the end of each groove, stopping any furthertravel of the flanges in a rearward direction, thus preventing anynoticeable retracting movement of the guard 30 from the fully extendedposition.

Flanges 34 a and 34 c also work in cooperation to achieve the antitravelfunction. The groove 64 which is engaged by the inner lip 32 of flanges34 a and 34 c, has a sufficient width to allow the inner lip to travelslightly rearward during engagement of the antitravel mechanism, suchthat the flanges 34 a and 34 c do not interfere with the function of theantitravel mechanism of flanges 34 b and 34 d. If the inner lip 32 werenot allowed to travel in the groove 64, any rearward force on the guard30 would displace the guard positioning mechanism 50 before theantitravel mechanism could engage.

Yet another cooperation feature between flanges 34 a and 34 c, and theantitravel mechanism can include an inner surface of flanges 34 a and 34c each including a slight relief (not shown), which prevents the flangesfrom possibly displacing slightly outwards when inner lip 32 is engagedin the groove 64, due to flange thickness and the surface of pin 62.Likewise, flanges 34 b and 34 d are slightly shorter than flanges 34 aand 34 c, allowing the mechanical engagement to occur within the chamberhousing without interference.

The resistance provided by the leaf spring 52 engagement with the fullyextended detent slot 56 is sufficient to hold the guard positioningmechanism 50 in place when an external force is applied to the fullyextended guard 30. The guard positioning mechanism 50 remains inposition as the guard 30 is slightly displaced rearward activating theantitravel mechanism incorporated into the coupling mechanism asdescribed above. In this embodiment, the slight rearward displacementprior to full activation of the antitravel mechanism is negligible.

In a second version of the first embodiment, the guard positioningmechanism 50 of the user actuator can be constructed with an integralcantilever beam spring to provide the spring biasing mechanism forcingdetent engagement. In this version as shown in FIGS. 8A through 8F, theguard positioning mechanism 50 has an integral cantilever beam 70,secured at a first end and flexing at an opposite end upon which aninclined projection 72 is used to provide the spring biasing mechanism.This plastic molded spring can be used to replace the leaf spring 52 andmaintain each position of the guard 30 by an engagement between themolded spring and the first or second detent 54 and 56 located in thelower body contour wall 24.

In this second version, the guard positioning mechanism 50 includes atleast one inclined projection 72, wherein the incline (i.e., 45 degrees)is provided to allow easy entry and removal from the detents. Theintegral cantilever beam 70 firmly presses the projection 72 against thelower body contour wall 24 when sliding between extended and retractedpositions. As noted above, the lower body contour wall 24 includes afirst and second detent 54 and 56, located at opposite positions withinthe substantially hollow chamber such that the projection 72 engages thefirst detent 54 when the guard positioning mechanism 50 is in a fullyretracted position, and engages the second detent 56 when the guardpositioning mechanism 50 is in a fully extended position. Slidablemovement of the guard positioning mechanism 50 between positions throughthe use of a prevailing force is opposed by a slight resistance createdby the projection 72 in contact with the lower body contour wall 24. Theslight resistance provided allows the guard 30 to maintain a positionwhen the user releases the external control 58, and prevents the guardfrom sliding freely.

When constructed having similar spring characteristics, the use of theintegral cantilever beam 70 and the inclined projection 72 eliminatesthe need for a metal spring component. The spring biasing mechanismtherefore becomes part of the user actuator (i.e., raised operatorcontrol 58 and guard positioning mechanism 50), and all can be made fromone piece of material. This reduces variability in the “feel” whenmoving the guard positioning mechanism 50 between positions (i.e., inand out of detent engagements). In the above embodiments, when the metalleaf spring component 52 is assembled into the guard positioningmechanism 50, the dimensions of the metal spring component can bealtered due to the nature of the assembly method required. Additionally,the metal leaf spring can have a reduced cycle life relative to theplastic molded spring, and can deform after few detent engagements.

Combining the spring biasing mechanism and the user actuator into one,thus eliminating one of the two parts, allows for tighter tolerancesbetween the remaining components (i.e., detent and spring biasingmechanism). Furthermore, the variability incurred as part of theassembly method between the metal leaf spring component and the useractuator is also removed. The tighter tolerances and removal of theassembly method added variability ensures smooth and consistent detentengagement. As with the above embodiments, the smoother detentengagements also provide feedback to the user through an audible clickand a mechanical snap that can be felt through the user actuator.

The integral cantilever beam 70 and inclined projection 72 can bemodified in shape and form, and still act as the spring biasingmechanism. For example, in yet another version the cantilever spring 70and inclined projection 72 can be molded into the lower body contourwall 24 (i.e. handle base) and the detents 54 and 56 placed into theguard positioning mechanism 50 of the user actuator, thereby reversingthe locations of these two features.

In still another embodiment, a fully circular guard may also be used toshield the exposed blade. In a second embodiment of the presentinvention, the guard is fully circular at the distal end, which allows alarger portion of the guard to remain exposed when fully retracted. FIG.9A is a perspective view of a second embodiment of the present invention100 with the guard 130 in a retracted position to expose a blade 140 foruse. The guard 130, when in the retracted position, forms a smooth,uninterrupted handle surface between distal and proximal endssubstantially as described in the first embodiment. When not in use, theguard 130 can be extended, as shown in FIG. 9B, to safely shield theblade 140.

FIG. 10 is an exploded perspective view of a second embodiment of thepresent invention. The view of FIG. 10 includes a first and second bodycontour wall 122 and 124, formed to assemble as a handle body 120 anddefine a substantially hollow chamber within the body 120 to house aconcealable portion of the guard 130. The first and second body contourwalls 122 and 124 each provide a recess, which when assembled, creates aslot 128 extending rearward from the distal end and accessing thechamber to allow protrusion of a raised operator control 158 for theguard 130. The distal end of the first and second body contour wall 122and 124 also includes an outer surface having a dimpled texture,extending from the distal end to a point slightly before the midpoint ofthe access slot 128. Additionally, as shown FIGS. 9A and 9B, the outercircumference surface area of an exposed portion of guard 130 alsoincludes a dimpled texture, such that when fully retracted, the dimpledtexture surface area is unbroken about the distal end of the body 120.

The distal ends of both the first and second body contour wall 122 and124 further include a reduced outside diameter for receiving the exposedportion of guard 130. Specifically, as the guard 130 is slidablyretracted, the fully circular exposed portion of guard 130 is receivedby the reduced outside diameter of the first and second body contourwall 122 and 124, until reaching a shoulder at the fully retractedposition. Seating the guard 130 against the shoulder of the reducedoutside diameter forms the smooth, uninterrupted handle surface betweendistal and proximal ends described above.

In the second embodiment of the present invention, the guard 130 iscontrolled to travel between a fully extended and fully retractedposition via an external protrusion 158 accessed through channel 128 ina manner substantially as described in the first embodiment. As shown inFIGS. 10 and 11, each position is maintained by an engagement between aspring 152 within a body cavity of the guard positioning mechanism 50and either a first or second slot 154 and 156, provided along rails ateither side of the hollow chamber within the body 120. The chamber,slots and rails are formed as described below, and serve to provide aslidable engagement surface for the guard to travel between fullyextended and fully retracted positions.

As shown in FIGS. 10 and 11, the first and second body contour wall 122and 124 assemble to define a substantially hollow chamber within thebody 120 to house the guard 130 which contains a spring 152 mountedbeneath a saddle 160 that is driven between rails on either side of thechamber. The guard 130 includes a fully circular distal end, provided toshield the blade 140 fixedly secured to blade holder 126) when fullyextended. An elongated member 132 extends rearward from the fullycircular distal end, and provides a platform supporting a saddle 160, aplate 136, an external protrusion 158 and a contoured end 134.

As shown in FIG. 11, each body contour 122 and 124 provides a first andsecond rail 162 and 164, along the inner wall of the chamber. The firstrail 162 is provided to engage the spring 152, as described in greaterdetail below. The second rail 164 is provided to engage the saddle 160,and maintain saddle alignment between fully extended and retracted guardpositions.

The first rail 162 is provided between saddle 160 and spring 152. Thespring 152 is mechanically attached to the bottom of the saddle 160 andincludes an extension having a 90 degree angle oriented to firmly pressagainst the upper surface of the first rail 162 when sliding betweenextended and retracted positions. The upper surface of the first rail162 of each contour wall 122 and 124 includes a first and second slot154 and 156, located at opposite positions along the substantiallyhollow chamber such that the spring 152 engages the first slot 154 whenthe guard 130 is in a fully retracted position, and engages the secondslot 156 when the guard is in a fully extended position. Slidablemovement of the guard 130 between positions is opposed with a slightresistance created by the spring 152 contact with the rail surface oneither side of the chamber. Additional features can be provided toprevent possible twisting of the fully circular distal end of the guard130 when fully extended. As shown in FIG. 10, the second body contourwall 124 can include a recessed groove 166 extending along the surfaceof the distal end beneath the elongated member 132. A plate (not shown),extending below the elongated member, can be used to slidably engage therecessed groove 166 of wall 124, providing alignment and support for theelongated member 132 and the fully circular distal end of the guard 130when traveling between fully extended and fully retracted positions.

Once the spring 152 engages either the first or second slot, the guard130 is locked in place. To disengage the spring 152 requires the user toapply slight perpendicular pressure to the external protrusion 158 untilthe spring 152 is disengaged from the slot, and thereafter, a parallelforce can be used to slidably move the guard 130 to a new position. Asnoted above, the spring 152 is oriented to firmly press against thesurface of the first rail when sliding between extended and retractedpositions, and maintain a position in the first or second slot when atextended or retracted positions. Therefore to allow the application ofslight perpendicular pressure required to disengage the spring 152 fromeither slot 154 or 156, the guard 130 includes the elongated member 132extending into the chamber and contacting a surface via a contoured end134. The guard 130 also includes a slight notch 138 at a point betweenthe saddle 160 and a plate 136 extending downward and contacting thespring 152.

To disengage the spring 152 from either slot 154 or 156, a slightperpendicular pressure applied to the external protrusion 158 istransferred to the elongated member 132. The contact at the contour 134,and the slight notch at 138, allows the perpendicular pressure todisplace the plate 136 downward, forcing the spring 152 from the slot.The plate 136 is slightly narrower than the spring 152, therefore theplate can freely move between rails and deflect the wider spring 152from contact with rail 162. As with the first embodiment, the protrusion158 can provide simple and safe one finger control of the guard 130.

In a modified version of the second embodiment (not shown), the firstand second body contour wall assemble to define a substantially hollowchamber within the body to house the guard which contains a springmounted beneath a saddle that is driven between rails on either side ofthe chamber substantially as described above. However, in this version,the spring is oriented to contact the bottom of the chamber and firmlypress the saddle against the surface of at least one rail provided whensliding between extended and retracted positions. Each contour wallincludes a first and second slot, located at opposite positions along atleast one rail within the substantially hollow chamber such that thesaddle, under pressure from the spring, engages the first slot when theguard is in a fully retracted position, and engages the second slot whenthe guard is in a fully extended position. Once the saddle engageseither the first or second slot, the guard is locked in place. Todisengage the saddle requires the user to apply slight perpendicularpressure to the external protrusion until the saddle is disengaged fromthe slot, and thereafter, a parallel force can be used to slidably movethe guard to a new position.

In a third embodiment of the present invention, the slidable movement ofthe guard positioning mechanism is achieved using a plunger mechanism,as often associated with any of several ballpoint pen mechanisms thatadvances a pen tip through the push of a button. FIGS. 12A and 12B areperspective views of the third embodiment of the present invention witha plunger type operator control and the guard in an extended andretracted position, respectively. Such mechanisms 255 typically involvea user activated plunger to advance a pen tip outward or to retract apen tip inward in a longitudinal direction. The use of a pen mechanismat the proximal end of the device can provide an alternative to the sideslot described in regards to the above embodiments. This would allowfurther variations in the single handed use of the embodiments describedabove.

Such a pen mechanism would utilize features similar to those in currentpens to move the blade guard back and forth, as opposed to extending andretracting a pen tip. A user actuator can be located on the proximal endof the device that functions like a pen mechanism, i.e. to click theguard in or out. Specifically, the mechanism could include a simple,single cylindrical member 250 extending from the proximal end opening254 along the axis of the device body 220, and operate in a click-in andclick-out fashion with an extension/retraction mechanism 255 as known tothose skilled in the art. Alternatively, the mechanism could include acylindrical member extending from the proximal end along the axis of thedevice and being divided into two or more members, or segments, 256 and258 as shown in FIG. 12C. The divided members, when together, form thesingle cylindrical member; however each member can move relative to theothers and provide an action unique to the movement of the particulardivided member. Related divided function mechanisms can be found inmulti-colored ballpoint pen mechanisms, which include different pushbutton segments to extend different colors of pen tips from a singledevice.

In this example, various guards could be fabricated to fit inside and/oroutside the body and/or chamber of the handle and still achieve thedesired coverage of the blade. By disposing the guard partially insideand/or outside the device, the handle or body of the device can beconstructed with a smaller diameter, or allow for the guard to bettershield the blades described above or other blade geometry.

The guards could further comprise various shapes which can provide bladeshielding at various places or of various strengths. Specifically,different guard shapes may provide different strength characteristics,and further allow the guard to withstand higher forces. These may alsoallow for a smaller guard, or enlarged guard distal end, therebyminimizing visual interference with the blade while providing maximumprotection from blade contact resulting in a blade stick. Such a guarddesign can be either completely inside, outside or a combination ofboth, and the guard and enlarged guard distal end can be either open orclosed, and can achieve full-circumference protection or providealternative means to shield a blade depending on blade design. Inexamples which provide a semi-circular guard, the guard and enlargedguard distal end can still include other shapes, such as, but notlimited to, triangle, square and/or box shapes, and still other shapeshaving multiple facets or sides, all with or without a circular orradius cross section, but which still provide shielding for blades ofdifferent geometry.

Returning to FIGS. 12A and 12B, the spring biasing mechanism thatprovides detent engagement within such a pen mechanism can include anynumber of configurations, such as the leaf spring and a cantilever beamdescribed above, or a compression/extension spring. In still anotherexample, the spring, such as the leaf spring, could be replaced withanother spring biasing mechanism forcing detent engagement. In eachexample, the spring could provide a sufficient resistive force necessaryfor the guard function. In the embodiments of the present inventiondescribed above, the guard and enlarged guard distal end can beconfigured to withstand forces up to 3 lbs. in one example. Where such aspring biasing mechanism is used, the required applied force wouldtypically be equal to or greater than the force which the guard canwithstand. In yet another example, the spring biasing mechanism may beused to reduce the force required to move the guard back and forth, orto strengthen the guard design in each embodiment described above.

Unlike prior blade shielding mechanisms, embodiments of the presentinvention can withstand an inadvertent force. Such protection can beprovided by utilizing an internal locking feature (i.e. a third detent)as described in greater detail above. These embodiments do not disengageor allow the guard to move from the shielding state to the non-shieldingstate by any reasonable inadvertent force applied longitudinally to theguard. Each embodiment therefore is able to implement a lock-outfeature.

The embodiments of the present invention can be constructed of anysuitable material, including a number of materials which can beautoclaved for repeated use. For example, where the embodiments areprovided with metal blades and suitable body materials, multiple usesare possible using steam autoclave processes. In such examples, apreferred blade 40 and spring 52 material includes stainless steel (formetal spring versions only), and the body 20 and guard positioningmechanism 50 can be constructed of polyetherimide. The guard 30 can beconstructed of transparent or opaque polycarbonate. Where the leafspring 52 is omitted and replaced with an integral cantilever beam 70and inclined projection 72, the beam and projection can also beconstructed of a polyetherimide.

Where repeated use is not desired, other blade materials can beprovided, including silicon, and the body 20 can be constructed ofautoclave intolerant materials, such as high impact polystyrene. The useof high impact polystyrene will result in the substantial destruction ofthe device when autoclaved, thereby preventing reuse. In suchapplications, the leaf spring 52 can be constructed of stainless steel(for metal spring versions only), and the guard positioning mechanism 50and guard 30 can be constructed of polyetherimide and polycarbonate,respectively.

Although only a few exemplary embodiments of the present invention havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims.

What is claimed is:
 1. A surgical knife safety handle, comprising: ahandle body having a longitudinal axis; a knife holder affixed to saidhandle body and carrying a knife blade at a distal end of said handlebody; a guard longitudinally movable with respect to said handle bodybetween extended and retracted positions, said guard having a distalportion configured to at least partially cover said knife blade whensaid guard is in said extended position and to expose said knife bladefor use when said guard is in said retracted position, said guardfurther having a proximal portion, each of said distal and proximalportions of said guard being at least partially external to said handlebody in both the extended and retracted positions of said guard; and aprotrusion extending externally from said guard to be engageable by auser, said protrusion being carried by said guard for allowing a user tolongitudinally move said guard between said extended and retractedpositions to selectively cover or expose said knife blade; wherein saiddistal portion of said guard is configured to adjoin said handle bodywhen said guard is in said retracted position; wherein where said handlebody and said guard adjoin, said guard has, an outermost circumferencesubstantially the same as an outermost circumference of said handle bodythereby providing a circumferential outer surface with said handle bodywhen said guard is in said retracted position, said guard and said,handle body each having a surface with a pattern, a rearmost portion ofsaid guard pattern being in radially circumferential alignment with arearmost portion of said handle body pattern when said guard is in saidretracted position; wherein said guard is releasably lockable in saidextended and retracted positions, and said protrusion is depressible bya user to release the locking of said guard at said extended andretracted positions; and wherein said guard carries a spring to assistin locking said guard at said extended and retracted positions, saidspring being connected at distal and proximal ends thereof to internalstructures of said guard.
 2. A surgical knife safety handle as claimedin claim 1, wherein said protrusion is rigidly affixed to said proximalportion of said guard.
 3. A surgical knife safety handle as claimed inclaim 1, wherein said distal portion of said guard is at least partiallycylindrical.
 4. A surgical knife safety handle as claimed in claim 1,wherein said distal portion of said guard is at least partially circularwhen viewed along said longitudinal axis.
 5. A surgical knife safetyhandle as claimed in claim 1, wherein said handle body comprises atleast one of a slot, groove, rail or plate to guide said longitudinalmovement of said guard.
 6. A surgical knife safety handle as claimed inclaim 1, wherein said guard comprises at least one of a slot, groove,rail or plate to guide said longitudinal movement of said guard.
 7. Asurgical knife safety handle as claimed in claim 1, wherein said handlebody has a longitudinal opening for movably receiving said proximalportion of said guard.
 8. A surgical knife safety handle as claimed inclaim 1, wherein said handle body has a distal portion narrower in atleast one transverse dimension than a proximal portion of said handlebody, said distal portion of said handle body being received by saiddistal portion of said guard when said guard is in said retractedposition.
 9. A surgical knife safety handle as claimed in claim 1,wherein portions of said guard and said handle body engage to preventtwisting of the distal portion of said guard when said guard is in theextended position.
 10. A surgical knife safety handle as claimed inclaim 1, wherein said extended and retracted positions of said guard aredefined by selectively engageable internal structures of said guard andsaid handle body.
 11. A surgical knife safety handle, comprising: ahandle body having a longitudinal axis; a knife holder affixed to saidhandle body and carrying a knife blade at a distal end of said handlebody; a guard longitudinally moveable with respect to said handle bodybetween extended and retracted positions, said guard having a distalportion configured to at least partially cover said knife blade whensaid guard is in said extended position and to expose said knife bladefor use when said guard is in said retracted position, said guardfurther having a proximal portion, each of said distal and proximalportions of said guard being at least partially external to said handlebody in said extended and retracted positions of said guard; and aprotrusion extending externally from said guard to be engageable by auser, said protrusion being carried by said guard; wherein said distalportion of said guard is configured to adjoin said handle body when saidguard is in said retracted position; wherein the adjoining portions ofsaid handle body and said guard form a circumferentially continuousouter surface, said guard and said handle body each having a surfacewith a pattern, a rearmost portion of said guard pattern being inradially circumferential alignment with a rearmost portion of saidhandle body pattern when said guard is in said retracted position; andwherein said guard is releasably lockable in said extended and retractedpositions, and said protrusion is depressible by a user to release thelocking of said guard at said extended and retracted positions.
 12. Asurgical knife safety handle as claimed in claim 11, wherein said distaland proximal portions of said guard are both configured to adjoin saidhandle body to provide a substantially continuous outer surface withsaid handle body when said guard is in said retracted position.
 13. Asurgical knife safety handle as claimed in claim 11, wherein theproximal portion of said guard is narrower in at least one transversedimension than said distal portion of said guard.
 14. A surgical knifesafety handle as claimed in claim 11, and wherein said handle body has alongitudinal opening for movably receiving said proximal portion of saidguard.
 15. A surgical knife safety handle as claimed in claim 11,wherein said handle body has a distal portion narrower in at least onetransverse dimension than a proximal portion of said handle body, saiddistal portion of said handle body being received by said distal portionof said guard when said guard is in said retracted position.
 16. Asurgical knife safety handle, comprising: a handle body having an outercircumference and a longitudinal axis, said handle body furthercomprising a slot in said outer circumference and extending along saidlongitudinal axis; a knife holder affixed to said handle body carrying aknife blade at a distal end of said handle body; a guard longitudinallymoveable with respect to said handle body between extended and retractedpositions, said guard having a distal portion configured to at leastpartially cover said knife blade when said guard is in said extendedposition and to expose said knife blade for use when said guard is insaid retracted position, said guard further having a proximal portionslidably disposed in said slot of said handle body; and a protrusionextending externally from said guard to be engageable by a user, saidprotrusion being carried by said proximal portion of said guard forallowing a user to longitudinally move said guard between said extendedand retracted positions to selectively cover or expose said knife blade;wherein said distal portion of said guard is configured to abut saidhandle body when said guard is in said retracted position; wherein wheresaid handle body and said guard abut, said guard has an outermostcircumference substantially the same as an outermost circumference ofsaid handle body thereby providing a mating circumferential outersurface with said handle body when said guard is in said retractedposition, said guard and said handle body each having a patternedsurface area, proximal-most portions of said respective patternedsurface areas being in radially circumferential alignment with eachother when said guard is in said retracted position; wherein said guardis releasably lockable in said extended and retracted positions, andsaid protrusion is depressible by a user to release the locking of saidguard at said extended and retracted positions; and wherein said guardcarries a spring to assist in locking said guard at said extended andretracted positions, said spring being connected at distal and proximalends thereof to internal structures of said guard.
 17. A surgical knifesafety handle as claimed in claim 16, wherein said protrusion is rigidlyaffixed to said proximal portion of said guard.
 18. A surgical knifesafety handle as claimed in claim 16, wherein said extended andretracted positions of said guard are defined by selectively engageableinternal structures of said guard and said handle body.
 19. A surgicalknife safety handle, comprising: a handle body having a longitudinalaxis; a knife holder affixed to said handle body and carrying a knifeblade at a distal end of said handle body; a guard longitudinallymovable with respect to said handle body between extended and retractedpositions in each of which said guard can be releasably locked, saidguard having a distal portion configured to at least partially coversaid knife blade when said guard is in said extended position and toexpose said knife blade for use when said guard is in said retractedposition; a protrusion extending externally from said guard to beengageable by a user, said protrusion being carried by said guard; and aspring carried by and longitudinally moved with said guard to saidretracted and extended positions to assist in locking said guard at saidretracted and extended positions; wherein said distal portion of saidguard is configured to abut said handle body when said guard is in saidretracted position; wherein a portion of where said handle body and saidguard abut contributes to a circumferentially continuous outer surface,said guard and said handle body each having a surface pattern, aproximal-most portion of said guard surface pattern being in radiallycircumferential alignment with a proximal-most portion of said handlebody surface pattern when said guard is in said retracted position; andwherein said protrusion is depressible by a user to release the lockingof said guard at said extended and retracted positions.
 20. A surgicalknife safety handle as claimed in claim 19, wherein said guard has aproximal portion, and said protrusion is carried by said proximalportion of said guard.
 21. A surgical knife safety handle as claimed inclaim 20, wherein said protrusion is rigidly affixed to said proximalportion of said guard.
 22. A surgical knife safety handle as claimed inclaim 1, said guard further having a proximal portion narrower in atleast one transverse dimension than said distal portion of said guard.